You could side load it, but would more than likely require a mouse and keyboard to use it as most sideloaded apps that don't support the Google laidback launcher do not accept the remote OK button as a screen touch.

The apps will come, Android TV is going to be a massive product as it is built into some TV's right now (Sony, Philips, and Sharp atm). Not to mention the Nexus devices, Amazon FireTV (different app store), Nvidia Shield TV, Plus numerous cheap models as well.